<html>
<head>
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"/>
<meta charset="utf-8" />
    <title>图片上传—显示</title>
    <meta name="description" content="">
    <meta name="keywords" content="">
    <meta name='viewport' content="width=device-width,initial-scale=1.0,user-scalable=no,
	      maximum-scale=1.0,
	      minimum-scale=1.0">
<style>
.mybtn{
    width:100px;
    height:30px;
    display:inline-block;
    background-color:rgb(91,183,91);
    border:1px solid rgb(91,183,91);
    border-radius:3px;
    color:white;
    font-size:14px;
    font-family:微软雅黑;
    cursor:pointer;
    text-align:center;
    vertical-align: center;
    box-shadow:0px 0px 1px 1px rgb(91,160,91);
    }

.mybtn:hover{
    background-color:rgb(91,160,91);
    border-color:rgb(91,160,91);
    color:white;
    text-decoration:none;
    }   
.myinp{
    width:100px;
    height:30px;
    display:inline-block;
    border:1px solid rgb(209,232,250);
    border-radius:2px;
    }
#div4bm{
    padding-top:15px;
    margin-right:15px;
    }
    #mybutton{
    margin-left:100px;
    }
#myimg{
    width:164px;
    height:164px;
    }
</style>
</head>
<body>
<div class="content" style="margin-top:100px;height:200px;">
    <div id="div4bm" style="float:left;">
    <!--input[button] 触发 file click事件-->
    <input type="button" value="选择文件" id="mybutton" class="mybtn"  onclick="Id('file').click();" />
    <!--file 隐藏起来  触发onchange事件-->
    <input type="file" name="file" accept="image/png,image/jpg,image/jpeg"  id="file" onchange="changeToop();" style="display:none;" />
    </div>  
    <!--图片展示区域-->
    <div style="float:left;">
        <!--设置默认图片-->
        <img id="myimg" src="http://sandbox.runjs.cn/uploads/rs/72/huvtowwn/zanwu.png"/>
    </div>
</body>
<script>
//定义id选择器
function Id(id){
return document.getElementById(id);
}
function changeToop(){
    var file = Id("file");
    if(file.value==''){
        //设置默认图片
    Id("myimg").src='http://sandbox.runjs.cn/uploads/rs/72/huvtowwn/zanwu.png';
    }else{
        preImg("file","myimg");
    }
}
//获取input[file]图片的url Important
function getFileUrl(fileId) { 
    var url; 
    var file = Id(fileId);
    var agent = navigator.userAgent;
    if (agent.indexOf("MSIE")>=1) {
    url = file.value; 
    } else if(agent.indexOf("Firefox")>0) { 
    url = window.URL.createObjectURL(file.files.item(0)); 
    } else if(agent.indexOf("Chrome")>0) {
    url = window.URL.createObjectURL(file.files.item(0)); 
    } 
    return url; 
} 
//读取图片后预览
function preImg(fileId,imgId) { 
var imgPre =Id(imgId);
imgPre.src = getFileUrl(fileId); 
} 
</script>
</html>